A Split Between Personality's
by Savitar-X-Supergirl
Summary: Summary: Kara gets exposed to Black Kryptonite and now her evil self is out there causing trouble. What will she do? How is she gonna find her evil self? But what happens when the evil Kara takes the extrapulator and goes to Earth-1 and Kara follows? Will she enlist the help of TeamFlash? Note: This takes place somewhere around Season 2 of Supergirl and Season 2 of The Flash.
1. Chapter 1

**Chapter: 1**

**The Arctic Tundra**

"I don't understand Ma'am, why come all the way out here to one of Mr. Luthor's warehouses?" asked a Cadmus agent while walking in the snow behind the leader of Cadmus with a few other agents.

"Because Mr. Romariz, my son has something here that I require." stated the Lillian Luthor the fearless leader of Cadmus as she wraps her jacket around herself to protect against the freezing cold of the Arctic.

"Finally, were almost there." Lillian said as they stopped and looked at the warehouse in the distance through the snow. "But why all the way out here?" asked another agent as they started walking.

Lillian sighs, "That's what we are here to find out." she said.

**10 Minutes Later**

After walking for 10 minutes they finally made it to the warehouse and stood in front of a door. "Break it open." Lillian ordered one of the agents while he takes a torch from the bag and burn the lock off.

Once the lock is burned they open the door and take their flashlights, "What are we looking for Ms. Luthor." asked an agent as he opened case.

"Well according to my sons journal, there is a type of rock that will work on the kryptonian." Lillian replied as she opened a case. "Ah…..here we go." she stated as she lifted up the object.

"What is that Ms. Luthor?" asked Romariz as he shined his flashlight to see a black rock.

Lillian let out a chuckle, "This is what will bring Supergirl down to her knees. It's back Kryptonite, according to my son it's supposed to split a kryptonian's bad side from the good side." she said as she put it back in the case and closed it.

"You mean, it splits the kryptonian into two different sides? One good and one bad?" asked an agent as he walked towards the leader. "Exactly." Lillian replied as she took the case, "Come on we have what we came for." she said as they walked out of the warehouse.

**National City**

Kara Danvers (aka) Supergirl was flying around the city enjoying the sun that's currently out, it was a beautiful day Kara thought to herself as she turned on her back folding her arms under her head a float. It was a good day. She woke up on time, made sure everything was ready for game night tonight, and her fighting crime duties were all done. Just as she was getting ready to head back to her place she hears a sound of gunshots and alarm sounding. A Bank Robbery. Kara sat up then flew at her top speed to get to the scene of the crime.

When she got there she crashed through the ceiling and was in the Lobby, she saw 4 guys in black ski masks as they all turned towards her and fired their weapons at her, she watched with a smile as those bullets just bounced off of her. "You should know those don't work on me right?" Kara asked as she sped over to them and knocked them out.

The hostages all cheered and ran out the doors after they all said thank you to Supergirl for rescuing them. Kara then turned to the thieves and get them ready for the police, but then she saw a strange black rock next to one of the guys. Curious she reached down to pick up, and as soon as she touched it she felt intense pain and there was a blast that sent her flying through the wall into an office.

"Ow." she said as she grabbed the wall and stood up, "Well, that's new." she commented as she walked back over to where she was at and took the end of her cape and pick up the rock flying it to the DEO.

Once she landed in the DEO Alex came over, "Hey are you okay? Winn was reading some energy surge at the bank a few minutes ago." she asked glad to see her sister was alright.

"Yeah. I'm fine, but I think that this rock was the cause of that energy surge." said Kara as she handed the rock over to Alex, "But it's weird when I touched it hurts, like when I'm around Green Kryptonite but it doesn't weakened me it just….I don't know." she added as she looked at her sister for answers.

Alex sighed, "We'll look into it Kara, go home and take a day." she said with a smile walking away. Kara decided that she would take her sisters advice and fly back to her apartment.

But when Kara flew through her window and landed she gasped at the strange person on her couch. But this person was and look exactly like her but the suit is black instead of blue, and was sitting on the couch with her legs crossed, leaned back with her arms crossed with a smile. "Hello, Kara. We got so much to discuss." said the Kara look alike.


	2. Chapter 2

**Chapter: 2**

Kara was stunned by how can they be another her, "Who are you?"she asked her other self. "Well I'm you, well not exactly. I'm all of that anger and darkness that you have hidden inside you. Too afraid to let it show. But when you touched that rock it brought me out." said the Kara look alike as she got up and walked around the couch towards the kitchen.

But then the other Kara remembered the rock in the bank, "That rock in the bank. What ...what is it?" she asked her other self trying to understand this new information.

The other Kara sighed and replies, "It's called black kryptonite, it splits a kryptonians two sides. The Good and The Bad. I'm the bad version of you. Wow this is really good." she said as she took a bite of a pizza.

"I...I Never heard of this Black Kryptonite." Kara stated as she walked over to her bad self.

The other Kara shook her head and put the pizza down, "Because, Lex Luthor had it in his warehouse to use against our dear cousin. But since he's rotting in a cell, his lovely mother Lillian found the rock and was planning on using it against you which she already did. She wants to bring me out to turn the city against you." she said.

"So the bank robbery, it was a trap to lure me so I will touch this Black Kryptonite." she sighs, "This is just great. Okay you need to go back, tell me how to….to….. Get rid of you so you can't hurt anyone." Kara said.

The other Kara laughed, "You gotta be kidding. Kara, these people, these humans, they don't trust you, they were ready to hang you by your neck. They don't deserve us. Join me Kara, and together we will be unstoppable." she said as she walked up to Kara.

"I'm sorry I can't let you do that." Kara stated as she was getting to a defensive stance. The other Kara rolled her eyes, "At least I tried. Sorry Kara." she commented as she pushed Kara sending her through the window.

Kara flew back towards the window and sped over to her counterpart and tossed her through the wall to the bedroom cracking another wall, "Stop this. Now. Your gonna hurt them." she said.

The other Kara grunted as she got up, "Fine. If not these Humans. Maybe those humans on another Earth, like Earth-1 perhaps?" she asked holding up the extrapulator. "Bye. Bye. Kara." she added as she pressed a button and jumped through, Kara jumped in after her and wrap her arms around her evil self as it closed behind her.

**Earth-1**

Barry, Cisco, HR, Joe and Iris were all in the breach room when a breach opened, "Guys someone is coming through." Cisco yelled as the team got into defensive positions, but was stunned when something came out at fast speeds hitting the wall behind Cisco making him jump. What the team saw was shocking, two Kara's fighting each other, "I will not let you hurt these Humans." one Kara said.

The other Kara shrugged, "Watch me!" she commented as they both came at each other as they collide both of them flew up through the ceiling as the Team runs to the cortex. "What the hell is happening? They are two Kara's which one is which." Cisco said as he typed a few keys. But before he could find out there was a crashing noise, they looked up and watched as one of the Kara's crashed through the ceiling landing on the floor cracking it under her weight.

Barry got down so he could look, "It's Kara. The real one. Hey Kara you okay?" Barry asked as Kara woke up. "B..Barry? What…..Oh my god." she exclaimed as she stood up and looked around. "I'm so sorry. Did I or other me hurt you guys?" she asked worried about her friends.

Joe nodded, "No Kara were fine. What was that? Who was that girl? He asked as the team was waiting on an answer. Kara sighed, "It's a long story but she's me. Well not exactly me, just the evil me. The dark version of me. You see there's this rock. It came from Krypton when it exploded, it landed on earth. It can split a kryptonians two sides. One good. One Bad. She's the bad." Kara explained as she paced back and forth, " We need to find her guys. She's…...if she's the bad version of me we need to find her and fast." she added.

"Or what?" Iris asked. "You know how powerful I am. Guess what my powers can do when it's in the wrong hands." Kara told her as the team all sighed and groned. "This is gonna be bad." Cisco commented.

"Okay Kara. Right now we need to know everything about…..you, her I mean." HR told her as the team agreed. Kara nodded and explained everything that went on from the bank robbery to the conversation she had with herself to transporting here. "I'm so sorry for bringing her here. I didn't even know she had the device until it was too late."

Iris came up to her and place a hand on her shoulder, "It's okay Kara. Right now we just need to find her. Is there anything we can use against her? I mean she's you right? So do you have any weaknesses" Iris asked.

"Yes. There's a green rock called Kryptonite. It's like the black but this one is green. It weakens me, it's painful, and if I'm exposed to it for a long time. I'll die." Kara told them. "I think that if you can use it against her then you can probably weaken here enough to get her into one of your cells in the pipeline." she added.

"Well where do we find one?" Joe asked. "No. No. Kara you said this rock can kill you. You sure you want to do that?" Barry asked wanting to know if she's sure about this. Kara sighed, "It's the only way to bring her down Barry." Kara told him.

HR raises his hand, "If you and her are connected and if we use this rock against her. Won't you feel the effects?" he asked. Kara nodded, "Yes, I will feel everything she's feeling. But I don't care I just want to get this over with." she said with confidence.

Barry nodded as Cisco says, "Uh...one problem. You said that this black rock split you guys up. How are we gonna put you two together." he asked.

"I will need to go back to my earth and get the Kryptonite. Will you guys be okay while I'm gone?" she asked afraid of leaving them with an evil her.

Barry nodded, "Go Kara. We'll be okay. Just hurry." he said as Kara nodded. Cisco made a portal as Kara jumped through heading back to her earth.


	3. Chapter 3

**Chapter: 3**

**Earth-38**

At the DEO everyone was doing their jobs when a portal opened in the middle of the room causing all the agents to draw their weapons as alarms went off. Alex and J'onn came out from their places. But they were stunned when they see Kara jump out of it, "Hey Guys sorry to scare you but it's important." she said as the portal closed behind her.

"Agents stand down." J'onn ordered as they all got back to what they were doing before. " Kara! Are you okay? What was that….that swirl?" Alex asked.

Kara sighs, "It's a long story. Which I have no time for. Do you still have that black rock I found at the bank?" she asked.

J'Onn nodded, "Yes but we still don't know nothing about it." he responded. "Well I do. I know what it does. It's called Black Kryptonite. It splits a Kryptonian two sides good and bad. So right there is an evil version of me out there and to out us back together we will need the rock." she told them.

Alex and J'onn were stunned, "What? Black Kryptonite? How come we haven;t heard of it before."

"Because Lex had it to use against Superman and now Lillian, CADMUS got a hold of it and planted that bank robbery as a trap to get me in contact with the rock letting my bad self out. Now I don't have time I need the rock now, I also need the green Kryptonite to take her down or something that will work on me if I turned." she demanded.

Alex ran to the lab to retrieve it, when she came back she gave it to Kara, "Where's the other version of you at?" she asked as an agent gave Alex a rectangle case and handed it to Kara. "This is what I used on you when you went crazy. No offense." Alex said.

"It's fine Alex, and she's not here on Earth. Well not this Earth, ever heard of the multiverse? Have Winn explain it to you. But think of it as another Earth." She commented as she took out her device and pressed the button and a portal formed. When she's getting ready to jump a hand grabs her arm, "I'm coming with you." Alex said not taking no for an answer.

"I'm sorry Alex. No. I need to do this. Besides you got things here to look after while I'm gone." Kara told her. "But how do you know that it's safe?" she asked worried for her sister.

"I have friends over there. Another Superhero I met. Besides, it's not my first time on his Earth. Remember what I told you about Barry Allen?" She said as she jumped through the portal as it closed behind her.

**Earth- 1**

Back in the cortex at STAR Labs team flash tries to find the other version of Kara when a portal opened and Kara jumped out with a big case and small led box. "Hey, I'm back. And Cisco I got you something that would work on my eveil me." she told him as she let the case down.

"Ooooohhhhh. Really? Let me see." he said as him and the team gathered around the case as Kara opened the box and took out the item that looked like a bazooka, but more powerful filled with the dwarf sun energy. "This is what will bring me down." she said.

"What does it do? And what happened to the kryptonite?" Cisco asked as he looked at the cannon with love.

Kara sighed, "Well, I remembered that there was something that was used on me once when I went bad and crazy because I was exposed to Red Kryptonite, but that's another story. This powers a star called Red Dwarf, under the sun we don't have out powers. I figured if we shoot her with this then she will lose her powers temporarily just enough to get her into your little prison cell. And Cisco I thought maybe you can build something that can contain her with this stuff."

Cisco nodded, "Oh yeah totally. I'll get to work on it. Don't worry Kara we'll find her." he said as Kara placed the cannon back in its case and closed it. She grabbed the lead box. "This contains the black kryptonite. When we catch her get me beside her and you put this in my hand and hopefully me and her will become one again." she said as she opened it, revealing a glowing black rock. "Why is it glowing?" Iris asked as she looked at the rock in awe.

"It does that when a kryptonian is near. There's multiple versions of Kryptonite: Green, Red, Gold, Blur, and now Black." she said as she stood up. "What does the others do?" Caitlin asked first time talking since Kara arrived., "The green is painful, and can weaken us, it can also kill us if we are exposed to it for too long. Red manipulates your mind, making you do bad things, turning evil. The gold takes away our powers, forever and can't get them back. Blue temporarily takes our powers away." she finished listing them off.

The team just looked at her shocked, "Wow!" Barry said being the first one to say something. "Must be tough being who you are with all those things out there." he added now a little worried for his friend.

Kara shrugged, "It's fine, as long as I stay away from them then I'll be okay. Cisco want to start on making a device that will hold a kryptonian?" Kara asked. Cisco nodded, "Sure, but how can you help? Do you know anything…" Cisco started to say but was interrupted.

"My birth father was a scientist Cisco, I think I can handle it." she commented as she followed a stunned Cisco taking the case and the rock with her.

**A Few hours Later**

Cisco and Kara had just walked back into the Cortex to announce that it's ready when an alarm sounded, Cisco ran to his computer and typed a few keys, "It's your double, she's causing trouble in Central Park." he announced to the team.

"Is the cuffs ready?" Barry asked Kara as she nodded, "Yea, they are ready to be used. It should hold a Kryptonian since it's made of the dwarf star that's used to strip our powers." she answered. "What if it doesn't work?" Caitlin asked, "What are we gonna do?" she added worried that they won't be able to defeat an alien as strong as Kara.

"Then, it's a good thing I brought this." Kara said as she took another led box, "This has green kryptonite in it. Led is the only metal that can contain the kryptonite without it affecting me we made bullets since she'll be on alert making sure we don't do anything she doesn't like." Kara said as she took the canon out of the case, "Oh can I shoot it. Please?" Cisco asked with a puppy dog face, "Alright, just be careful. It's alien tech. My tech from Krypton so be careful." Kara told him as she handed him the canon, "Cool." he whispered with a smile "Okay so are we ready?" Barry asked making sure everyone is ready to face an almost unstoppable alien. When the team nodded Kara, Barry, and Cisco walked out of the lab.


	4. Chapter 4

**Central City Park**

When Kara, Barry, and Cisco got to the park vis interdimensional portal, they saw Citizens screaming and running away in panic as the evil Kara fires her laser beams. "Oh My God…." Kara whispered as she saw the damage, "I….It's happening. My powers are being used for ...for this….." she added as she watched in horror.

Barry felt sorry and placed a hand on her shoulder, "Kara it's not your fault. We have to do this okay?" he assured her, Kara nodded, "I'll keep her occupied while you get ready to take her down." she said and flew up towards the other Kara, "NO…..STOP." she yelled at her other self.

The other Kara looked at her, "Well. Well. Well. Come join me? It's about time you come to your senses." she said with a smile.

"I didn't come here for that. I just need to know why you are doing this. They never did anything to you. To us." Kara said to her counterpart.

The other Kara look at her like she grew a second head, "What? You actually care for these humans? They despise us Kara. They're afraid of us. We were sent here to become gods." she tried to reason with the good Kara.

"Cisco you ready?" Barry asked as he watched Kara distract the other Kara. "I'm ready Barry. You handle the kryptonite. I got the red dwarf." Cisco replied through his comms. "Just let me know when." he added. "Now Cisco." Barry ordered as he saw a red energy beam hit the bad Kara as she and the other Kara screamed. The bad Kara fired her heat vision at the direction it came from and Barry heard a scream in his comm. "Cisco? Cisco, are you olay?" he asked worried about his friends, brother, and team mate.

"I...I'm good just got my shoulder, damn it hurts. Your turn Barry." he replied as Barry looked at the green rock in his hand and sped out and tossed the rock towards the bad Kara. But she saw it coming and used her heat vision to disintegrate it, "NO." Kara yelled as she reached for the rock as it connected with the heat vision creating a blast of green energy tossing the two kryptonian back knocking them both out.

"KARA." Barry yelled as he sped over to his friend and felt for a pulse, "She's alive. Check the other one." he ordered as he watched the green veins on her face, She groaned, "Hey. Hey you're gonna be okay." Barry told her as Cisco came through the coms. "The other Kara is okay and I got her in the cuffs. How's Kara?" he asked.

Kara winced and whimpered as he can tell she was in pain, "We need to get her back to STAR Labs. Both of them. Kara's in pain." he said as he carefully picked up his superfriend and sped back towards the lab.

When he got there he placed Kara on the gurney as Caitlin came in and gasped, "What happened to her?" she asked as she ran over and checked on Kara.

"Something went wrong with the plan. The other Kara saw it coming and tried to use her heat vision to destroy it but Kara touched it as the laser made contact and it blasted them apart. These green lines are the effects of the Kryptonite." he informed her.

"What do we do I don't know anything about aliens, especially Kryptonians." she said as she looked over Kara.

Kara winced and groaned, "S...un…...t ...the yellow ...sun. R..Radiat...ion from….." she swallowed down the pain and yelled as Barry know what she was saying, "Sun. She needs the radiation from the earth's sun." he told her.

"Mercury labs has sun lamps maybe…" Iris started to say but Barry sped away and came back with 2 sun lamps and turned them on. "All we have to do is wait and hope that she'll wake up." Caitlin said as they walked over to the screen, to watch what they recorded.


	5. Chapter 5

**An Hour Later**

It has been an hour since they went out to stop Kara's double. Team Flash was sitting around the computers watching Kara's counterpart hit the cell that was lined with the red sun. "It's so weird seeing another Kara." Cisco commented.

Barry was about to say something when they heard a groan, they all ran into the med bay and saw that Kara was waking up, "B..Barry?" she called as she opened her eyes. "Hey, Kara I'm here."He said coming up to the side of the bed, "Did we get her." she weakly asked.

Barry nodded, "Yeah we got her Kara. We got her." he replied as Kara smiled, "Good. Good." she said closing her eyes.

"How are you feeling?" Barry asked Kara as she opened her eyes again and take a deep breath, "I feel okay." She said as she slowly sat up with the help of Barry. "Where is she?" she asked wanting to be sure that they got her.

Barry sighs, "In the pipeline. You can come see for yourself if you feel up to it." He told her concern of the effects of the Kryptonite. Kara nodded and made her way off the bed with Caitlins help and walked slowly towards the Cortex.

"Hey look who it is." Cisco said as he came up and hugged her, "How are you feeling?" he asked as he let go.

"I'm feeling great Cisco. Can I see her?" she asked needing to see for herself. Cisco nodded as Kara followed him to the computers that showed a footage of the other Kara in a cell, "I lined it with the red dwarf star you told us about. It should hold her." he commented.

"Where's the green kryptonite?" Kara asked wondering where it went to.

"We looked everywhere in the park. There is no trace of Kryptonite. I think it was destroyed when you double's heat vision made contact." Barry answered her question. Kara nodded, "What do you remember Kara?" Joe asked testing to see if she remembered the fight.

Kara nodded and walked around, "I remember the plan, me flying up to her. I remember feeling pain when Cisco fired the cannon, I remember everything up to the part where you tossed a kryptonite…..What happened with the Kryptonite again?" she asked.

"Oh uh...when I tossed it hoping that it would land on your double and weaken her, but she must've seen it and forced her heat vision and then you touched the rock just as the laser made contact creating a blast that sent you guys back knocking you guys out." Barry told her as Kara nodded taking in all the information.

"Thank you everyone. I'm sorry again for bringing her here." she said feeling bad, "I'm also sorry for what my double did to the people of this city. My powers are dangerous and it was in the wrong hands." she told them hoping they'll not be mad.

Iris came up and hugged Kara, "It's not your fault Kara. Just be glad it's gonna be fixed." she told Kara as she let go and gave the alien a smile.

"Thanks Iris." Kara said as she takes a deep breath, "Uh ... where's the Black Kryptonite. I'm ready to merge us back together." she said wanting to get this over with.

"Are you sure Kara? Are you up for it?" Barry asked still worried about his friend whom he came to like.

Kara nodded, "I need to get her out of here. So yes Barry I'm sure." she told him. Cisco brought the rock out, "Here it is." he said holding it for her to look at. "I'll get the other Kara." Joe said as he took the red cuffs with him.

Kara was standing in the middle of the room waiting as she watched Joe walk in with her bad counterpart. Once she was placed beside Kara Barry handed his friend the black rock. "Had fun while it lasted Kara." said the other Kara with a smile.

Kara ignored her as she grabbed the rock and winced as orange lines begin to show on her hands, she grunted as she took her double's hand and slammed the rock and they both screamed in pain as purple surround them, the team watched in shock as the bad Kara merging with their friend. When it was over Kara gasp as she fell to the floor dropping the rock and landing on her hands and knees.

"Kara." Iris yelled as she ran over to the kryptonian and helped her up. "Are you okay?" she asked. Kara nodded and took a deep breath, "Yeah, Just…..whoa that hurt." she said as she chuckled along with the team.

They were all in the breach room to send their friends off after having dinner with the West Family and the team, "It was good to see you Kara. Considering the circumstances." Barry said as he hugged Kara. She hugged back, "It was good seeing you too Barry." she said as she let go. After she was giving a hug from each member of the team she turned around and pressed the button on her device as a portal appeared and she walked through as it closed behind her.

"You have some interesting friends Barr." Joe said after the portal closed behind their alien friend. "Yes I do Joe. Yes I do." he replied as him and the team walked out of the room heading home.

**Earth-38**

Back on Kara's earth Alex Danvers was in her sisters apartment when a portal opened scaring her making her draw her weapon but relaxed when Kara jumped out. "Hey Alex." Kara greeted as Alex hugged her. "Are you okay? Did you get her?" Alex asked her sister as the portal closed behind Kara.

"Yeah, we got her Alex and yes I'm okay."she said to Alex leaving out the part where she was knocked out because she doesn't want Alex to worry. "Well I'm glad you're okay. Now since your back let's go ahead with game night." Alex said with a smile. Kara laughed as she joined her sister.

**Hope you guys enjoyed this story. This was the hardest story I ever did. So comment if you like it. Thank You for reading!**


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